Ionic liquids (IL) are organic salts that are commonly liquid at room temperature. ILs have also been defined as molten salts having a melting point below 100° C. Recent interest in room temperature ionic liquids has increased due to unique characteristics of those compounds, such as a unique solubility, negligible vapor pressure, a wide electrochemical window and good thermal stability. Due to the negligible vapor pressure of ILs, they have been identified as environmentally friendly as they would not contribute to air pollution or to the generation of potentially toxic emissions when used as a solvent. As a result of these advantageous characteristics, ILs have potential use in a number of applications, including but not limited to synthesis, as both solvents and catalysts; energy storage, as electrolytes; extraction of radioactive materials, metals and organic liquids; polymer processing; cellulose processing; and gas separations. However, due to the vast amount of structural configurations possible for an ionic liquid, estimated at up to 1018 available compounds, selection of appropriate compounds for the various applications can be intimidating.
ILs include triazolium salts, which consist of two isomeric compounds having aromatic 5-membered rings with three nitrogen and two carbon atoms on the ring as the cation. The two isomers are typically referred to as 1,2,4- or 1,2,3-triazolium salt based on the position of the nitrogen atoms, e.g., 1,2,3- refers to a salt where the three nitrogen atoms are adjacent to one another on the ring. Heterocyclic compounds based on 1,2,3-triazoles have been widely used due to their high biological activity, in antiviral, antimicrobial, antifungal medicines and agricultural chemicals. The 1,2,3-triazole heterocycle is commonly synthesized via Cu(I)-catalyzed 1,3-dipolar cycloaddition and Ru-cat of azides and alkynes, resulting in a 1,4-di-substituted 1,2,3-triazole core and 1,5-di-substituted 1,2,3-triazole core, respectively. However, synthesis and use of tri-substituted 1,2,3-triazolium salts in various applications has not been thoroughly explored.
For example, certain five and six-membered aromatic heterocyclic ILs have been identified as potential candidates in gas separation processes, particularly in U.S. Pat. No. 6,579,343, issued to Brennecke, et al. However, relative to the vast number of potential ILs, very few ILs have found widespread use for most applications, and gas separations in particular.